In many commercial vehicles equipped with an Automated Manual Transmission (AMT), gear shifts can be a challenging transient. In an AMT, the execution of an upshift (shift to the next higher gear, resulting in a net decrease in engine speed) or a downshift (shift to the next lower gear, resulting in a net increase in engine speed) is often paced by the transient response of the engine. While significant increases in fuel may be provided to quickly accelerate the engine to a higher speed needed for a downshift, in an upshift the engine fuel can only be reduced to zero, and deceleration is dictated by engine friction. This deceleration rate can often cause shift times to be in excess of one second. When the driver is attempting to accelerate the vehicle hard, a one second interruption in engine torque can feel very significant. Moreover, attempts to improve engine efficiency often involve reductions in engine friction, which results in even longer deceleration rates.
Accordingly, it is desirable to provide reduced deceleration times during upshifting. It is further desirable to control torque ramp up to improve shift quality, and enhance engine acceleration during downshifting.